Traditionally, implant dentistry involves the restoration of one or more teeth in a patient's mouth using artificial components. Such artificial components typically include a dental implant, an abutment connected to the implant, and a prosthesis or artificial tooth secured to the abutment. The process for restoring a tooth is typically carried out in three stages.
The first stage involves implanting the dental implant into the living bone of a patient's jaw. The oral surgeon first accesses the patient's jaw bone through the patient's gingival or gum tissue and removes any remains of the tooth to be replaced. Next, the specific site in the patient's jaw where the implant is to be anchored is made or widened by drilling and/or reaming to accommodate the width of the dental implant to be implanted. Then, the dental implant is inserted into the hole in the jaw bone.
The dental implant itself is typically fabricated from pure titanium or a titanium alloy. Such materials are known to produce osseointegration of the implant fixture with the patient's jaw bone. Osseointegration is a process by which the living bone surrounding the implant will proliferate and grow into whatever spaces exist between the implant and the bone surfaces. In this way the newly generated bone tissue encases the implant to securely hold or anchor it in place.
The dental implant fixture typically included a body portion and a collar. The body portion is configured to extend into and osseointegrate with the alveolar bone and includes a hollow threaded bore through at least a portion of the body portion and extending out to the collar. The top surface of the collar typically lies flush with the crest of the jawbone bone. The hollow threaded bore typically receives a dental abutment, either directly or by virtue of a separate securing device such as an abutment screw. The abutment (e.g., a final abutment) typically lies on the top surface and extends through the soft tissue, which lies above the alveolar bone. Some dental implants have collars that extend above the crest of the jawbone and through the soft tissue. The abutment ultimately supports the final tooth prosthesis. The prosthesis is typically secured to the abutment either by a cement or other adhesive or by use of a fastener such as a screw.
After the implant is initially installed in the jaw bone, a healing screw (a cover) is secured over the exposed proximal end in order to seal the internal bore of the implant body. The patient's gums are then sutured over the screw covered implant to allow the implant site to heal and to allow desired osseointegration to occur. Complete osseointegration typically takes several months, ending this Stage 1 phase.
In the second stage, the surgeon reaccesses the implant fixture by making an incision through the patient's gum tissues. The healing cover screw is then removed, exposing the proximal end of the implant. The hollow threaded bore of the implant is thoroughly cleaned and dried. The surgeon then attaches a temporary cap secured by a cover screw, which is screwed directly through the healing cap into the hollow threaded bore of the implant. The gingival tissues are again closed around the cap and sutured in place. To accurately record the position, the orientation and the shape of the final abutment, the surgeon can take a mold or impression of the patient's mouth. The impression, which includes the implant abutment sites, is then sent to the laboratory and is used to create a plaster or stone model which is a direct duplication of the patient's mouth. This provides the information needed to fabricate the prosthetic replacement tooth or any required intermediate prosthetic components.
Based on the model from the second stage, the technician will construct the final restoration by: (1) removing the sutures; (2) removing the healing cap and the healing cap screw; (3) thoroughly cleaning and drying the exposed hollow threaded bore of the implant body; (4) screwing the solid abutment into the implant body's hollow threaded bore; and, (5) securing the final cosmetic prosthesis to the patient's mouth abutments with a dental adhesive cement.
Implants of various tapers and with various thread profiles are known in the art. For example, U.S. Pat. No. 5,427,527 describes a conical implant design that is placed into a cylindrical osteotomy site in order to induce bone compression at the coronal aspect of the implant, i.e. at its widest end. Other thread profiles and patterns are known in the art. The most common design involves a symmetrical, V-shaped appearance such as that illustrated in U.S. Pat. No. 5,897,319. A variable thread profile is disclosed in U.S. Pat. Nos. 5,435,723 and 5,527,183 which is mathematically optimized for stress transfer under occlusal loads. U.S. Pat. Nos. 3,797,113 and 3,849,887 describe dental implants with external thread-like features having a flat shelf facing the coronal end of the implant.
While such prior art dental implants have been successful, there is a continuing desire to improve a dental implant's ability to osseointegrate with the alveolar bone and to improve the stability of the dental implant within the alveolar bone.